12.3 Pain Management & Analgesics

Pain Assessment

Pain is whatever the experiencing person says it is, existing whenever they say it does (McCaffery's definition). It is subjective and individualized — vital signs may be normal in severe chronic pain, so never use vitals alone to judge pain. Use a structured history:

OLDCARTS: Onset, Location, Duration, Character, Aggravating/Alleviating factors, Radiation, Timing, Severity.

Validated scales:

• Numeric Rating Scale (0–10) — standard for verbal adults
• Wong-Baker FACES — children ≥3 years and patients with language barriers
• FLACC (Face, Legs, Activity, Cry, Consolability) — nonverbal children and impaired adults
• PAINAD — advanced dementia
• CPOT / BPS — critically ill, ventilated patients

Reassess after every intervention within the expected onset window (about 15–30 minutes IV, 60 minutes oral). Evaluate function — ability to cough, deep breathe, ambulate, and sleep — not just the number.

WHO Analgesic Ladder

• Step 1 (mild, 1–3): non-opioids — acetaminophen, NSAIDs ± adjuvants
• Step 2 (moderate, 4–6): add a weak opioid or low-dose strong opioid
• Step 3 (severe, 7–10): strong opioids — morphine, hydromorphone, fentanyl ± non-opioids and adjuvants

Dose by the clock for persistent pain (scheduled, not only PRN), use the oral route when possible, and individualize titration. Adjuvants belong at every step.

Multimodal Analgesia

Modern practice, especially in enhanced recovery after surgery (ERAS) pathways, uses multimodal analgesia: combining agents that act at different points of the pain pathway (acetaminophen + NSAID + regional block + gabapentinoid ± low-dose opioid) to improve relief and reduce total opioid exposure. Because the drugs work by different mechanisms, lower doses of each can be used, lowering the side-effect burden of any single class. Breakthrough pain — transient flares over a controlled baseline — is treated with short-acting rescue doses, and recurring breakthrough pain signals that the scheduled regimen needs re-evaluation rather than just more PRN doses.

Non-Opioid Analgesics

Acetaminophen

Maximum 4 g/day from all sources in healthy adults; limit to 3 g/day (or less) in older adults, hepatic impairment, malnutrition, or regular alcohol use. Combination products (e.g., hydrocodone/acetaminophen) count toward the total — hidden acetaminophen is a classic exam trap. Toxicity causes hepatic necrosis; the antidote is N-acetylcysteine.

NSAIDs

Ibuprofen, naproxen, ketorolac, celecoxib. Cautions:

• GI — bleeding and ulceration; give with food; risk rises with age, steroids, anticoagulants
• Renal — reduce renal perfusion; avoid in chronic kidney disease, dehydration, and with ACE inhibitors (the "triple whammy": NSAID + ACE-I/ARB + diuretic)
• Cardiac — increased MI/stroke risk; avoid after CABG (boxed warning) and use cautiously in heart failure (sodium and fluid retention)
• Ketorolac is limited to 5 days of use because of GI/renal risk

Opioids and Equianalgesia

Opioid classes: full mu agonists (morphine, hydromorphone, fentanyl, oxycodone), partial agonists (buprenorphine), and agonist-antagonists (nalbuphine — can precipitate withdrawal in opioid-dependent patients). Meperidine is avoided, especially in renal failure, because its metabolite normeperidine accumulates and causes seizures.

Equianalgesia: when rotating opioids, calculate the total 24-hour dose, convert using an equianalgesic table (oral morphine 30 mg ≈ IV morphine 10 mg ≈ oral hydromorphone 7.5 mg ≈ IV hydromorphone 1.5 mg), then reduce the new drug by 25–50% for incomplete cross-tolerance. Exact conversions are provider/pharmacy territory; the nurse's tested role is recognizing why the new dose is intentionally lower.

Opioid Safety

PCA Pumps

With patient-controlled analgesia (PCA), only the patient presses the button. PCA by proxy — family members or nurses dosing a sleeping patient — bypasses the built-in safety that a sedated patient stops pressing, and has caused fatal respiratory depression. Verify pump programming with two clinicians at setup and every change.

Monitoring for Respiratory Depression

Assess sedation level before respiratory rate — excessive sedation precedes hypoventilation. The Pasero Opioid-Induced Sedation Scale (POSS) runs from S (sleeping, easy to arouse) through 4 (somnolent, minimal response to stimulation — stop the opioid, support respirations, give naloxone). A respiratory rate alone misleads: a patient breathing 12/min but difficult to arouse is in danger. Risk factors: opioid-naïve status, first 24 hours of therapy, sleep apnea, COPD, renal failure, concurrent sedatives.

Naloxone

Naloxone reverses opioid respiratory depression: dilute and titrate in small IV increments (e.g., 0.04–0.4 mg) to restore ventilation without full reversal and abrupt withdrawal pain. Its half-life (~30–90 minutes) is shorter than most opioids — re-sedation (renarcotization) is expected, so monitor for at least 2 hours after the last dose and anticipate repeat dosing or an infusion. Long-acting opioids and fentanyl patches make this worse; remember a removed patch keeps delivering drug from the skin depot for 12–24 hours.

Side-Effect Management

• Constipation — the one opioid side effect to which patients never develop tolerance; start a stimulant laxative (senna) ± stool softener prophylactically, plus fluids, fiber, and ambulation
• Nausea — usually transient; antiemetics early
• Pruritus — often histamine-mediated, not a true allergy; antihistamines help
• Urinary retention and sedation — monitor and dose-adjust

Adjuvant Analgesics

• Gabapentinoids (gabapentin, pregabalin) — first-line for neuropathic pain (burning, shooting, diabetic neuropathy, postherpetic neuralgia); renal-dose and taper off
• TCAs (amitriptyline, nortriptyline) — neuropathic pain; watch anticholinergic effects in older adults
• Duloxetine — neuropathic and musculoskeletal pain
• Corticosteroids — bone pain, nerve compression in palliative care

Safe Disposal and Diversion Awareness

Teach patients to dispose of unused opioids through take-back programs or authorized collectors; the FDA flush list applies to high-risk drugs like fentanyl when take-back is unavailable. Never share opioids, store them securely, and never flush patches without folding them adhesive-to-adhesive. Nurses must also practice diversion prevention: waste partially used controlled substances with a witness, never carry others' access codes, and recognize that diversion endangers patients whose pain then goes untreated.